1. Field of the Invention
The present invention relates to networks, and more particularly to non-disruptive data capture.
2. Background of the Invention
Data-capture in a communications network typically requires dedicated and specialized equipment, and is not incorporated in a port attached to the communications network. Specialized data-capture equipment typically has abundant buffer space for the data-capture and can keep pace with all traffic in a communications network. However, many classes of problems—such as network and topology discovery, automated configuration, and intelligent device diagnostics—require data-capture but do not require keeping pace with the communications network itself.
Various protocols are used for networks. Fibre channel is a set of American National Standard Institute (ANSI) standards, which provide a serial transmission protocol for storage and network protocols such as HIPPI, SCSI, IP, ATM and others. Fibre channel provides an input/output interface to meet the requirements of both channel and network users.
Fibre channel supports three different topologies: point-to-point, arbitrated loop, and fibre channel fabric. The point-to-point topology attaches two devices directly. The arbitrated loop topology attaches devices in a loop. The fibre channel fabric topology attaches host systems directly to a fabric, which are then connected to multiple devices. The fibre channel fabric topology allows several media types to be interconnected.
Fibre channel is a closed system that relies on multiple ports to exchange information on attributes and characteristics to determine if the ports can operate together. If the ports can work together, they define the criteria under which they communicate.
In fibre channel, a path is established between two nodes where the path's primary task is to transport data from one point to another at high speed with low latency, performing only simple error detection in hardware.
FC-AL is one fibre channel standard (incorporated herein by reference in its entirety) that establishes the protocols for an arbitrated loop topology. In an AL loop (per the FC-AL fibre channel standard) various devices can send data to each other. An arbitration cycle (using the “ARB” primitive) determines which device gets access. The priority scheme itself is defined by the standard. A device (e.g. device A) seeking access to another device (device B) sends an ARB primitive. If device A wins arbitration then it sends an OPN primitive and establishes a connection with device B. Device B sends an R_RDY primitive indicating that credit is available for a frame. Thereafter, frames are transferred.
Each port has a loop port state machine (“LPSM”) and in conventional implementation, the LPSM must be at a certain state to send or receive data.
Unlike a traditional communications port, a Data-Capture port may receive data outside of typical network-specific hand shaking. For example, in a FC-AL topology, a traditional port may receive data only if the LPSM is in one of several specific states and only if sufficient Buffer-to-Buffer Credit is available, but a Data-Capture port may receive data regardless of these conditions. A Data-Capture port may also receive data destined for another port. Data-Capture ports copy data from a network, but do not follow network hand shaking, and do not participate as a traditional communications port.
In order to capture all data based on specific criteria, Data-Capture ports include a large set of buffers, which are typically expensive, and are separate from a traditional communications port.
FIG. 2 shows an example of a traditional implementation (200) of a traditional port and a data capture port. State machines 201 and 203 operate with limited buffers 206 and 205 respectively. Port 202 includes a data capture state machine and uses a large set of buffers 204. This makes the use of data capture ports very expensive in commercial products.
Therefore, what is required is a process and system that allows data capture function without using expensive buffers.